Add Wintun support (#289)

wintun/device.go

@@ -0,0 +1,23 @@
+//go:build windows
+
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
+ */
+
+//NOTE: this file was forked from https://git.zx2c4.com/wireguard-go/tree/tun/tun.go?id=851efb1bb65555e0f765a3361c8eb5ac47435b19
+
+package wintun
+
+import (
+	"os"
+)
+
+type Device interface {
+	File() *os.File                 // returns the file descriptor of the device
+	Read([]byte, int) (int, error)  // read a packet from the device (without any additional headers)
+	Write([]byte, int) (int, error) // writes a packet to the device (without any additional headers)
+	Flush() error                   // flush all previous writes to the device
+	Name() (string, error)          // fetches and returns the current name
+	Close() error                   // stops the device and closes the event channel
+}

wintun/tun.go

@@ -0,0 +1,212 @@
+//go:build windows
+
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2018-2021 WireGuard LLC. All Rights Reserved.
+ */
+
+//NOTE: This file was forked from https://git.zx2c4.com/wireguard-go/tree/tun/tun_windows.go?id=851efb1bb65555e0f765a3361c8eb5ac47435b19
+// Mainly to shed functionality we won't be using and to fix names that display in the system
+
+package wintun
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"sync"
+	"sync/atomic"
+	"time"
+	_ "unsafe"
+
+	"golang.org/x/sys/windows"
+
+	"golang.zx2c4.com/wintun"
+)
+
+const (
+	rateMeasurementGranularity = uint64((time.Second / 2) / time.Nanosecond)
+	spinloopRateThreshold      = 800000000 / 8                                   // 800mbps
+	spinloopDuration           = uint64(time.Millisecond / 80 / time.Nanosecond) // ~1gbit/s
+)
+
+type rateJuggler struct {
+	current       uint64
+	nextByteCount uint64
+	nextStartTime int64
+	changing      int32
+}
+
+type NativeTun struct {
+	wt        *wintun.Adapter
+	name      string
+	handle    windows.Handle
+	rate      rateJuggler
+	session   wintun.Session
+	readWait  windows.Handle
+	running   sync.WaitGroup
+	closeOnce sync.Once
+	close     int32
+}
+
+var WintunTunnelType = "Nebula"
+var WintunStaticRequestedGUID *windows.GUID
+
+//go:linkname procyield runtime.procyield
+func procyield(cycles uint32)
+
+//go:linkname nanotime runtime.nanotime
+func nanotime() int64
+
+//
+// CreateTUN creates a Wintun interface with the given name. Should a Wintun
+// interface with the same name exist, it is reused.
+//
+func CreateTUN(ifname string, mtu int) (Device, error) {
+	return CreateTUNWithRequestedGUID(ifname, WintunStaticRequestedGUID, mtu)
+}
+
+//
+// CreateTUNWithRequestedGUID creates a Wintun interface with the given name and
+// a requested GUID. Should a Wintun interface with the same name exist, it is reused.
+//
+func CreateTUNWithRequestedGUID(ifname string, requestedGUID *windows.GUID, mtu int) (Device, error) {
+	wt, err := wintun.CreateAdapter(ifname, WintunTunnelType, requestedGUID)
+	if err != nil {
+		return nil, fmt.Errorf("Error creating interface: %w", err)
+	}
+
+	tun := &NativeTun{
+		wt:     wt,
+		name:   ifname,
+		handle: windows.InvalidHandle,
+	}
+
+	tun.session, err = wt.StartSession(0x800000) // Ring capacity, 8 MiB
+	if err != nil {
+		tun.wt.Close()
+		return nil, fmt.Errorf("Error starting session: %w", err)
+	}
+	tun.readWait = tun.session.ReadWaitEvent()
+	return tun, nil
+}
+
+func (tun *NativeTun) Name() (string, error) {
+	return tun.name, nil
+}
+
+func (tun *NativeTun) File() *os.File {
+	return nil
+}
+
+func (tun *NativeTun) Close() error {
+	var err error
+	tun.closeOnce.Do(func() {
+		atomic.StoreInt32(&tun.close, 1)
+		windows.SetEvent(tun.readWait)
+		tun.running.Wait()
+		tun.session.End()
+		if tun.wt != nil {
+			tun.wt.Close()
+		}
+	})
+	return err
+}
+
+// Note: Read() and Write() assume the caller comes only from a single thread; there's no locking.
+
+func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
+	tun.running.Add(1)
+	defer tun.running.Done()
+retry:
+	if atomic.LoadInt32(&tun.close) == 1 {
+		return 0, os.ErrClosed
+	}
+	start := nanotime()
+	shouldSpin := atomic.LoadUint64(&tun.rate.current) >= spinloopRateThreshold && uint64(start-atomic.LoadInt64(&tun.rate.nextStartTime)) <= rateMeasurementGranularity*2
+	for {
+		if atomic.LoadInt32(&tun.close) == 1 {
+			return 0, os.ErrClosed
+		}
+		packet, err := tun.session.ReceivePacket()
+		switch err {
+		case nil:
+			packetSize := len(packet)
+			copy(buff[offset:], packet)
+			tun.session.ReleaseReceivePacket(packet)
+			tun.rate.update(uint64(packetSize))
+			return packetSize, nil
+		case windows.ERROR_NO_MORE_ITEMS:
+			if !shouldSpin || uint64(nanotime()-start) >= spinloopDuration {
+				windows.WaitForSingleObject(tun.readWait, windows.INFINITE)
+				goto retry
+			}
+			procyield(1)
+			continue
+		case windows.ERROR_HANDLE_EOF:
+			return 0, os.ErrClosed
+		case windows.ERROR_INVALID_DATA:
+			return 0, errors.New("Send ring corrupt")
+		}
+		return 0, fmt.Errorf("Read failed: %w", err)
+	}
+}
+
+func (tun *NativeTun) Flush() error {
+	return nil
+}
+
+func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
+	tun.running.Add(1)
+	defer tun.running.Done()
+	if atomic.LoadInt32(&tun.close) == 1 {
+		return 0, os.ErrClosed
+	}
+
+	packetSize := len(buff) - offset
+	tun.rate.update(uint64(packetSize))
+
+	packet, err := tun.session.AllocateSendPacket(packetSize)
+	if err == nil {
+		copy(packet, buff[offset:])
+		tun.session.SendPacket(packet)
+		return packetSize, nil
+	}
+	switch err {
+	case windows.ERROR_HANDLE_EOF:
+		return 0, os.ErrClosed
+	case windows.ERROR_BUFFER_OVERFLOW:
+		return 0, nil // Dropping when ring is full.
+	}
+	return 0, fmt.Errorf("Write failed: %w", err)
+}
+
+// LUID returns Windows interface instance ID.
+func (tun *NativeTun) LUID() uint64 {
+	tun.running.Add(1)
+	defer tun.running.Done()
+	if atomic.LoadInt32(&tun.close) == 1 {
+		return 0
+	}
+	return tun.wt.LUID()
+}
+
+// RunningVersion returns the running version of the Wintun driver.
+func (tun *NativeTun) RunningVersion() (version uint32, err error) {
+	return wintun.RunningVersion()
+}
+
+func (rate *rateJuggler) update(packetLen uint64) {
+	now := nanotime()
+	total := atomic.AddUint64(&rate.nextByteCount, packetLen)
+	period := uint64(now - atomic.LoadInt64(&rate.nextStartTime))
+	if period >= rateMeasurementGranularity {
+		if !atomic.CompareAndSwapInt32(&rate.changing, 0, 1) {
+			return
+		}
+		atomic.StoreInt64(&rate.nextStartTime, now)
+		atomic.StoreUint64(&rate.current, total*uint64(time.Second/time.Nanosecond)/period)
+		atomic.StoreUint64(&rate.nextByteCount, 0)
+		atomic.StoreInt32(&rate.changing, 0)
+	}
+}